The invention relates to a sound-absorbing or noise-prevention element constructed in sheet form in particular and consisting of a hollow body with at least one perforated surface and a filling of sound-absorbing material. Elements of this kind are used, for example, in order to screen off residential areas and isolating estates from sources of noise, such as airports and roads subject to heavy traffic, etc. They can be employed for the purpose of reducing the echo occurring on enclosed premises or lowering the noise level in crowded rooms. In German Registered Design No. 1,857,655 a process is described in which, to protect inner rooms from noise emanating from exterior sources, windows are provided with blinds in which the slats consist of at least partly perforated strips of metal which enclose a cavity filled with sound-absorbing fibrous material. Blinds of this kind are expensive to produce, and their applications are strictly limited.
For use in the open air, German Registered Design No. 1,844,032 describes noise-screening panels which are made of a material resistant to the effects of the weather and which are to be used in comparatively large sizes. To increase the stability, these noise-screening panels can be erected with double sheets which are rigidified with respect to each other by means of sheet-connecting traverses, the space between them being filled with noise-inhibiting substance. The sound-absorbing capacity of such noise screening panels has proved inadequate; sound waves impinging on the front sheet, for example, can be directly transmitted to the rear sheet via the traversed. The sound-inhibiting substance, although protected from the effects of the weather by the fact that it is enclosed between them, is by-passed by the sound, for the same reason.
According to German Pat. No. 1,302,413, large-area sound-screening panels are to be formed by a multiplicity of narrow board-shaped elements consisting of a layer which is inserted, sprayed or stuck into grooves and which has a sound-absorbing effect. The board-shaped elements should be capable of being either combined to form dense panels or positioned obliquely in the manner of the slats of blinds. The drawbacks of this system are the unsatisfactory sound-absorbing capacity and the considerable mechanical sensitivity resulting from exposed or ever overhanging sound-absorbing layers, in addition to the expenditure involved in practice in rendering the structure sufficiently resistant to weather conditions. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a noise prevention or noise-absorbing element of the type described above which can be erected at only moderate expense, despite its high sound-absorbing capacity, and which can be used universally by reasons of its great stability and resistance to weather conditions.
With this and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.